Golf Terms Subscribe Golf Terms Ever wonder what all those golf terms mean? What’s a bogey? What is all this talk about the back side? How much does a free drop cost? Unless you know the answers to these questions, you had better read up here. We’ve tried to make it a little easier for you and even inserted a couple of funnies too. We’ve researched our massive memories (that is the 1st funny!) and come up with a whole bunch of golf terms to assist you on the course and in the clubhouse. That’s right, you can be that guy who knows all the cool things to say… read on! ACE – This is a term used when a golfer makes a hole in one! In other words, the tee shot is hit and it goes into the hole – how about that! ADDRESS – Contrary to popular belief, this is not where the mailman delivers to but it is the position of one’s body taken just before the golfer hits the ball. You will often hear the term “addressing the ball” which means the golfer is standing there preparing to hit the ball. ALBATROSS – An old British name for a double eagle. What’s that you say, two eagles?

No, it means you scored 3 under par on a single hole! In other words, you scored a 2 on a par 5 hole. It’s a very good score and doesn’t happen very often. APPROACH – This is a short or medium iron which is played into the green. Often referred to as an “approach shot”. APRON – The closely cut area just around the edge of the green. Often referred to as the “Fringe”. BACKSPIN – This is a reverse spin, which causes the ball to stop very quickly on the green. BACKSWING – The backward part of the swing starting from the ground and going back over the top of the golfer’s head. BAIL OUT – A shot played to the “safe” part of the course. For example if the flag is right next to the water and the golfer intentionally shoots away from the flag to avoid the water – thus “bailing out” BALL MARKER – A token or small coin which is placed directly just behind the ball in order to mark the position of the ball on the green. This is usually done to allow another player who is farther away to putt without hitting any other balls.

BALL RETRIEVER – A long pole with a scoop on the end of it used to get balls out of water hazards. BALL WASHER – Come on, this one is self explanatory. These are found all over the golf course usually at the tee boxes. They clean and wash your ball. BANANA BALL – A slice that curves in a banana like shape from left to right (for right-handed golfers). BASEBALL GRIP – Holding the golf club like one would hold a baseball bat. All 10 fingers are on the grip. BEACH – An expression for sandtrap. (i.e. I’m in the beach) BENT GRASS – Type of grass which is found in mostly in northern climates. BERMUDA GRASS – Now think about this one for just a minute. This is a type of grass found mostly in southern climates, as it is tougher and more resilient to harsh sunlight. Kind of like you would find in… that’s right Bermuda! You are a genius! BIRDIE – A score of 1 under par for a hole. (i.e.

a score of 3 on a par 4 hole) BITE – A term used for the action of the backspin on the ball stopping it very quickly on the green. BOGEY – A score of 1 over par on a hole. (i.e. a score of 5 on a par 4 hole) BUNKER – Another name for a sandtrap. CADDIE – A person who carries a player’s clubs during play and offers assistance in accordance with the rules. CARRY – The distance in the air that a ball must travel before it hits the ground. (i.e. you need 160 yards to carry the water means you need to hit the ball 160 yards in the air to clear the water) CASUAL WATER – No this is not water dressed in blue jeans and T-shirt but rather any temporary puddles of water on the course which are not supposed to be there, like say for instance after a rainstorm. There is no penalty for a player to move his ball out of casual water. CHIP SHOT – A short approach shot with a low trajectory usually hit from close to the green. CHIP IN – This happens when you hit a chip shot (see above) into the cup.

(Note: this is usually good!) CHOKE – This word has two meanings. One is to grip lower on the club than normal (you may hear the term “choke down” on the club) The other definition in golf (and most other sports) means to collapse under pressure (i.e. he “choked” under the pressure of the Master’s). CHOP – To hit the ball with a hacking motion or the word immediately after “pork”. CLUBHEAD – The hitting area of the golf club. CLUBHOUSE – The main building at the golf course where players usually go to have refreshments and tell about their 2 under par round (note: at times, you can actually see their noses grow!) COURSE RATING – The difficulty of a course. Usually the higher the course rating the harder it is. CUP – The thing in the hole that holds the flagstick. DEUCE – Hmmm, now lets see, if an ace is a hole in one, then a deuce must be a hole in two! That’s right Sherlock! It is a score of 2 on a hole! DIMPLE – The small round indentations on the golf ball.

A lot of really smart guys (some call them scientists) got together and figured out how many dimples would help the ball fly straight and true. DIVOT – A piece of ground that is taken up by the club after hitting the ball. A good golfer ALWAYS replaces his divots and tamps them back down so they will grow back again! DOGLEG – This is one of two things. It is either one of four things that Rover walks on or it is a hole that goes straight for a while then has a bend (or “dogleg”) to the left or right. You decide which fits here! DOUBLE BOGEY – A score of two over par for one hole. These are not very good! DOUBLE EAGLE – NO, this is NOT two eagles, but it is a good score for one hole! In fact it is an excellent score for one hole – three under par for one hole! (i.e. a two on a par five!) This is also referred to as an “albatross”. DOWNHILL LIE – The ball is on the downslope of a hill. When a right handed player addresses the ball his right foot will be higher than his left foot.

DRAIN – To make a putt (“drain it”). DRAW SHOT – This is when a right handed player hits a controlled hook, which goes from right to left. DRIVE – This is the term which means your tee shot. It is also usually the way you get to the golf course. DRIVER – This is the club known as the 1 wood. It is usually the club that hits the ball the farthest. It is also a person that very rich people have to haul them around. DROP – This is a way that you get the ball back in play after hitting a shot into the water or out of bounds. This also happens to waitresses when they carry too many plates. DUB – A poorly hit shot. I “dubbed” that shot. DUFFER – One who hits a lot of bad shots. Can also be called a “hacker”. EAGLE – This is a bird in real life, but in golf it means a score of 2 under par on a hole. (I.e. a score of 3 on a par 5 hole) FACE – This is what you see when you look in the mirror and it is also the part of the clubhead that makes contact with the ball.

FADE – This is a shot (for a right-handed golfer) which curves gradually from left to right. FAIRWAY – This is the area on the golf course which lies directly between the tee box and the green and is cut really short and maintained really nice. You want to hit from this area if at all possible. FAT SHOT – This is a shot which is not good. The club hits the ground behind the ball and results in a poorly struck shot that usually doesn’t go very far. FLAGSTICK – Come’on, you gotta know this one. FLUB – See dub above. FOLLOW-THROUGH – The continuation of the golf swing to the end. FORE – This is spelled differently than the number 4. This is the term yelled when one hits a shot toward another person on the golf course to alert him/her of impending doom from being hit by the ball. FOURSOME – A term given to a group of… come’on how many do you think players? (hint: 4!) FREE DROP – A drop that you don’t have to pay for, really that is correct, you get to drop the ball and don’t have to add a stroke to your score.

This can happen when there is casual water on the course or ground under repair. FRINGE – The closely cut area just around the edge of the green. FRONT SIDE – The first nine holes is usually referred to as the “front side”. GIMME – A term for a putt that is close enough to the cup that it will certainly be made so the other player says “it’s a gimme” and the player doesn’t have to putt it. However, he does need to add this stroke to his score! GRAIN – This is the direction that the grass on the green is growing. A golf ball will roll faster with the grain and slower against it. GREEN – This is a color and also the term used to describe the putting surface on the golf course. GRIP – This refers to either the part of the shaft by which the club is held by the golfer or the manner in which the golfer holds the club. (i.e. an overlapping grip) GROSS – The total number of strokes a player takes on his round. GROUNDING THE CLUB – Placing the clubhead on the ground behind the ball at address position. GROUND UNDER REPAIR – An area on the golf course that is being repaired.

Golfers are able to take a “free drop” if their ball ends up in ground under repair. HACKER – A golfer who is not very skilled. Same as a duffer. HANDICAP – The number of strokes a player may deduct from his actual (or gross) score to adjust his score to that of a scratch golfer. HAZARD – A hazard is any sand trap, lake, pond, bunker, etc. that may cause problems on the golf course. It is normally a good idea to avoid a hazard on the golf course. HEEL – What you tell your dog to do when walking him/her OR the part of the clubhead nearest the shaft. HOLE – A 4 inch round receptacle on the green that you try to get your ball into. HOLE HIGH – An approach shot which is even with the hole but off to one side. HOLE-IN-ONE – See ACE above. HOLE OUT – the process of a player completing the hole. HONOR – the privilege of hitting first on the next tee. The “honor” is gained by having the lowest score on the preceding hole.

HOOK – To hit the ball and have it curve gradually from right to left (for right-handed golfers). HOSEL – The hollow part of the clubhead that the shaft fits into. INTERLOCKING GRIP – A type of grip where the little finger of the lower hand is interlocked with the index finger of the upper hand. IRON – A club with a metal head which is not a wood! JAIL – A golfer’s term for a ball hit into a lot of trees which makes it very difficult to hit your ball out of…”in jail” JUNGLE – A golfers term for heavy rough or in the woods. (i.e. in the jungle) KICK – A golfer’s term for bounce. (I got a bad kick means I got a bad bounce) LAG – To putt the ball with the intention of leaving it short of the hole so that the golfer is able to have a very easy putt on the next shot. LATERAL HAZARD – Any hazard that runs parallel to the fairway. LIE – This is what you tell your wife when she asks if you went to work and you really went golfing OR it is the position that the ball ends up when it comes to rest on the ground.

LINKS – Another word for a golf course. This originally meant a seaside course. LIP – The top rim of the cup or what you have two of on your face. LOB SHOT – A shot that goes straight up in the air and stops very quickly on the green. LOCAL RULES – A set of rules for a particular golf course as determined by that course. LOFT – This is an apartment in England OR it is the angle of the clubface from vertical. MATCH PLAY – This is a form of competition by holes. Each hole is worth one point no matter how many strokes one player beats another by. MEDAL PLAY – This is a form of competition decided by the overall number of strokes. This may also be referred to as stroke play. MULLIGAN – An extra shot which your opponent MAY allow you to take if you hit a really bad first shot. NOTE: this is NOT the way we suggest to play golf. MUNICIPAL COURSE – A public course which is owned by a local government agency. NASSAU – A form of competition which breaks down the play into front nine, back nine and overall 18 holes. A point is allowed for each nine and the total 18.

NINETEENTH HOLE – Another term for the clubhouse or in particular the bar at the clubhouse. This is Waggle’s favorite hole! OFFSET – A club with the head slightly behind (or offset) the shaft. OUT-OF-BOUNDS – The area outside of the golf course limits in which play is prohibited. If you hit the ball out of bounds you must hit again from the same spot and take a penalty stroke. OVERCLUBBING – Using a club that will hit the ball farther than necessary. PAR – The number of stokes that is recommended to take to complete a hole (or 18 holes). PENALTY STROKE – An additional stroke which is added to a golfer’s score for a rules violation, going out of bounds, losing a ball, or various other situations. PIN – This is the flagstick or the pole that is in the cup. PITCH – A short high arcing shot that lands on the green and usually stops quickly. PITCH AND RUN – Same as a pitch but hit with a lesser lofted club which causes it to roll farther. PIVOT – The rotation of the shoulders, waist, and pelvis during the golf swing.

PLAYING THROUGH – The process of slower players in front of faster players allowing the faster players to move ahead of the slower group. PREFERRED LIE – A lie that may be improved by a player. PRO SHOP – The golf course shop operated by the golf pro. PROVISIONAL BALL – An additional ball which is hit in case the first ball can not be found. If the first ball is found, it is played. If the first ball is not found, the provisional must be played and the player is assessed a penalty stroke. PULL – A ball that is pulled (or hit) to the left of the target (for right handers). PUNCH THE GREENS – No we’re not mad and hitting the greens… this is another way to say the greens are being aerified. PUSH – A ball that is pushed (or hit) to the right of the target (for right handers). PUTT – A shot that rolls on the green hit with the putter. PUTTER – The club with a flat face used to putt. Often called the “flat stick” PUTTING GREEN – The surface area around the hole that is specially prepared for putting. RANGE – This is the area where you go to practice.

It usually has many stations to hit practice shots. READING THE GREEN – Determining which way the putt will curve based upon the slope of the green. ROUGH – Long grass area adjacent to the fairway. Normally you try to avoid the rough. ROUND – Complete 18 holes of golf. (i.e. a round of golf is the playing of 18 holes) RUN – The distance the ball will travel along the ground after it lands. SANDBAGGER – This is a golfer who purposely tells others that he is a worse golfer than he really is in order to gain an edge in competition. SAND TRAP – The common name for a sand hazard. These are areas that are filled with sand and should be avoided. SAND WEDGE – An iron normally used to hit the ball out of the sand. It can also be used on short pitch shots. SANDY – A player makes a sandy when he hits a shot out of the sand and sinks the following putt. SCRATCH GOLFER – A player who has a handicap of 0. This player will theoretically shoot even par or better every time out. SHORT GAME – The part of the game made up of chipping, putting and other shots around the green.

SHOTGUN START – A method of starting play where players go to every tee box on the golf course and hit their tee shots at the same time. Sometimes a horn is sounded to start play. SIDE – This is a term, which is interchangeable with the word “nine” as in front side which means the front nine or front nine holes. Now if you are really smart, you can also figure out that the back side is the back nine or last nine holes! SIDEHILL LIE – This refers to a lie when the ball is resting on a slope and the golfer’s feet are either above or below the ball. SLICE – This is either a piece of bread or a shot struck by a golfer which curves pretty severely from left to right (for a right handed golfer). SLOPE RATING – USGA term that represents the difficulty of a course for bogey golfers relative to the USGA Course Rating (which represents the difficulty for scratch golfers). The higher the slope, the more difficult the course plays for bogey golfers. Slope ratings range from 55 to 155 and 113 is considered average.

SNAKE – An award 🙁 given to a player in a friendly game when the player three putts. Whoever has the snake at the end of the round usually ‘gets’ to treat the other players to a beverage. STARTER – The person who is responsible for sending the groups of players off the first tee. Usually the starter is located somewhere close to the first hole. STIMPMETER – This is a device which is used to calibrate the speed of the greens. Often referred to as ‘stimp’. A reading of 5 to 11 is the normal range with 5 being slow and 11 being extremely (PGA) fast! STONY – You just stuck it next to the pin… congratulations on the stony. This is the shot you wiggle and grunt to try and make it go in because you hit it so close to the hole. STROKE – This is often used in the following context, “how many STROKES are you giving me” which means how many shots or additional swings are you giving me to even out the match. It can also be the term used for the actual process of swinging the club through the ball.

SUDDEN DEATH – This is a method of breaking a tied match by playing extra holes. The first player to win a hole is the winner. SUMMER RULES – Ordinary rules according to the rulebook. SWEET SPOT – The center point on the face of the club. When you hit it here it feels really good! TAKEAWAY – This is what a golfer does when he starts the backswing. TEE – This is the wooden (usually) peg which is used to hold the ball up for driving. It is also the term for the area where play begins on a particular hole (i.e. the third tee is where the third hole starts) TEXAS WEDGE – The term for the putter when it is used from off the green. THREESOME – Hmmm… now if you think about this you might just get it. Hint: it refers to three players playing in the same group. TIGHT FAIRWAY – A narrow fairway with not much area on either side to miss. TOE – This is a term for what you have on your feet OR it refers to the part of the club farthest from where it joins the shaft. TRAJECTORY – The flight path of the ball.

If it goes way up in the air it is referred to a high trajectory. TURN – To start the back nine holes. To “make the turn” means you have finished the 1st nine holes and are “turning” to the 2nd nine. UNDERCLUBBING – Using a club that does not provide enough distance to hit the ball to the intended target. UNPLAYABLE LIE – A lie from which the ball can not be hit. (i.e. it is up against a tree and the player can not hit it) WAGGLE – The movement of the clubhead just prior to the player taking a swing. WEDGE – An iron with a high loft used for short shots requiring a high trajectory. WHIFF – Swinging and missing the ball. WINTER RULES – Local golf rules that permit the player to improve the lie of the ball in the fairway. There may be additional winter rules allowed depending on the golf course condition. WOOD – A club (either wood or metal) which is used for shots requiring a lot of distance. WORMBURNER – A shot which skims very low along the ground. Thus killing any worms that may be poking their heads up.

A Brief History of Golf Ball Design, and Why You Shouldn't Hit People with Baseball Bats - Core77 Core77 3 Comments 51550 Views I once helped a career criminal move some things out of his basement—long story—and when we got to his golf clubs, he hit me (not literally) with this factoid: A golf club is apparently the ideal implement for casual, everyday interpersonal assault. "I thought [guys in your line of work] used baseball bats," I said, naively. "Nah," he said. "Those are too big and heavy. You come at me with a bat and I can take it away from you. But this"—he turned around and swung a golf club back and forth through the air, causing it to make a creepy whistling noise—"you don't see this coming, it's so fast. And you can't get it away from me. Look at the rubber grip on this thing." Ergonomically superior, he said, though in more colorful terms. Lastly he pointed out that if you get pulled over and the cops find a bat in your trunk, you get a second look; but a set of golf clubs never prompts questions.

Other than that story I have nothing revelatory to say about golf club design. Golf ball design, on the other hand, is pretty interesting. The first golf balls from the 14th Century were made out of wood, specifically beech, by carpenters using hand tools. They weren't perfectly round and it's safe to assume that they sucked. The 17th Century saw the slight design improvement of the featherie, a leather ball stuffed with bird feathers and stitched shut. But these things took forever to make, behaved differently when vet versus dry, and were also not perfectly round. In the mid-1800s, a guy named Robert Adams Paterson made the first molded ball. He discovered that the sap from a sapodilla tree, native to Malaysia, could be heated up, placed into a round mold and would then dry hard. Called the guttie, these were the first golf balls with mass-manufacturability, and with the added bonus that they could be reheated and re-molded if they went out-of-round. Then an interesting discovery was made. If you owned a guttie for a while, it got nicked and banged-up from regular use.

People subsequently observed that when you hit a nicked-up guttie versus a brand-new one, the roughed-up balls actually had a more consistent flight path. Well before the Wright Brothers or any knowledge of aerodynamics, regular folk observed that those little nicks helped stabilize the ball in flight. Golf ball manufacturers thus began etching, carving and chiseling different textures into guttie surfaces, trying to find the pattern most conducive to stable flight. By the late 1890s, a new type of golf ball had been created, by accident, by a visitor to B.F. Goodrich's rubber goods manufactory. A guy named Coburn Haskell had a golf date with Bertram Work, a Goodrich superintendent, and while Haskell was waiting for his buddy in the factory, he idly wound a bunch of rubber bands into a ball shape—and by bouncing it, discovered it contained a high amount of potential energy. Work and Haskell subsequently skinned the invention with the sap from a Balata tree, and the guttie became obsolete. Up until the early 1900s, all golf balls were patterned with raised protrusions. But then an anonymous inventor discovered that surface indentations were the way to go.

Now covered in dimples, the new 20th Century golf ball could be smacked into seriously controlled flight, and pros could even put backspin on it to make it stop more quickly upon landing. (It also probably led to some theretofore unseen dramatic shanking.) By the 1960s Balata and rubber was done away with and replaced with urethane skins and synthetic resin cores. And while that sounds boring as heck compared to some of the earlier innovations, as we shall see in the next entry, there is something surprising about the modern-day golf ball. The latest design news, jobs & events. Straight to you every other week. Join over 300,000 designers who stay up-to-date with the Core77 newsletter... Subscribe How Are Golf Balls Made? | Golfsmith How Are Golf Balls Made? How Are Golf Balls Made? by Brian Hill The dimples on a golf ball help it go farther. NA/Photos.com/Getty Images Types of Golf Balls How golf balls are made depends on when the ball was made. Ancient early balls differed significantly from the three-piece and four-piece golf balls of the modern era.

Modern balls must meet the specifications of the governing bodies of golf, the United States Golf Association and the R&A of St. Andrews, Scotland. Those specifications now match, but they didn't always. Between 1931 and 1988, the R&A sanctioned a ball size that was slightly smaller than that sanctioned by the USGA, meaning golfers played with a different-size ball in European events. Earliest Golf Balls The game of golf is defined by hitting a round object through a predetermined course into a hole. Scotland is credited with being the birthplace of the game. It's not possible to pinpoint the exact date golf was established, but the Scottish Parliament banned golf in 1457, indicating it was well-established by that time. However, hockey-like games were played even earlier with a club or paddle and a ball, stone or disk in France, Belgium and Holland. The stick was used to hit the ball towards a goal. Early golf balls in the 1400s were carved out of hard wood, and the game was played by all classes of people – from peasants to nobility – during that era. Leather Golf Balls One of the first golf ball innovations came about in 1618.

The "featherie" was a leather sack constructed of three pieces of leather sewn together and then stuffed with wet feathers, usually goose. When the feathers dried, they expanded and gave a rounded shape to the sack. The balls were then painted. The process was tedious, taking up to eight hours to stuff one ball. The balls didn't last long, either, because the leather was more fragile than wood. The advantage of the featherie was its superior flight ability. The innovation made golf a game for the rich, since the featheries were expensive and prone to damage. The First Rubber Golf Balls The game didn't get back to the common man until more than 200 years later, in the mid-1800s, when the gutta percha ball was invented from the newly discovered substance called rubber. "Gutties," as they were nicknamed, could be mass-produced by heating the rubber and pouring it into molds. The balls were hammered manually when it was discovered that the perfectly smooth balls didn't go as far when hit as did balls with small indentations. These indentations were the precursors of the dimples on modern golf balls. Natural and synthetic rubber remain the mainstay of the modern golf ball.

Modern Golf Balls The two-piece modern ball is formed by surrounding a spherical molded core made of rubber or synthetic rubber with a hard covering. The core is then placed in an injection mold. Hot plastic, either surlyn or urethane, is injected and forms a hard, dimpled coating around the core. The ball is painted, stamped with a logo, given a glossy coat and dried. Three-piece balls have a core center, a rubber covering of the core and a final coating. The rubber covering may be rubber string wrapped around the core. Four-piece balls have another covering over the first covering around the core that's not as hard as the final coating but not as soft as the rubber covering the core. The manufacturing process varies a bit in the exact composition and materials used, based on different manufacturers and whether the ball is made for distance or control. HOT PRODUCTS ON Golfsmith.com Aerospaceweb.org | Ask Us - Golf Ball Dimples & Drag Golf Ball Dimples & Drag Can you explain why a golf ball has dimples? If dimples reduce drag, why don't we see this surface feature on other aerodynamic shapes like airplane wings?

- question from Brent Obst & Andrew While few among us can deny that golf is one of the least exciting of all spectator sports, we aerospace engineers are fascinated by its aerodynamics! Even the non-golfers of the world are familiar with the shape of a golf ball, like that pictured below, and have probably wondered why its surface is covered with small indentations called dimples. The dimples of a typical golf ball Before explaining the purpose of dimples, we first need to understand the aerodynamic properties of a sphere. Let us start by looking at a smooth sphere without any dimples, like a ping-pong ball. If we lived in an ideal world without any friction, the air flowing around a smooth sphere would behave like that shown in the following diagram. In this figure, the angle θ represents position along the surface of the sphere. The leading edge of the sphere that first encounters the incoming airflow is at θ=0� while the trailing edge is at θ=180�. A position of θ=90� is the top of the sphere, θ=270� is the bottom, and θ=360� brings us back around to the leading edge.

Note that in this ideal situation, the air flowing around the sphere forms a perfectly symmetrical pattern. The streamline pattern around the front face, from 270� up to 90�, is the same as that around the back face, from 90� down to 270�. (a) Ideal frictionless flowfield around a sphere and (b) the resulting pressure distribution The lower half of this figure also displays the pressure distribution around the surface of the sphere, as represented by the non-dimensional pressure coefficient Cp. Positive (+) values of Cp indicate high pressure while negative (-) values indicate low pressure. It is the differences between high-pressure regions and low-pressure regions that create aerodynamic forces on a body, like lift and drag. However, this ideal flow pattern tells us something very interesting. Notice that the pressure at the front of the sphere, or θ=0�, is very high. This high pressure indicates that the incoming air impacting against the front face creates a drag force. Nonetheless, the pressure at the back of the sphere, or θ=180�, is also high and identical to that at the front.

This high pressure actually creates a thrust, or negative drag, that cancels out the drag on the front of the sphere. In other words, this theoretical situation tells us that there is no drag on a sphere! Early aerodynamics researchers were quite puzzled by this theoretical result because it contradicted experimental measurements indicating that a sphere does generate drag. The conflict between theory and experiment was one of the great mysteries of the late 19th century that became known as d'Alembert's Paradox, named for famous French mathematician and physicist Jean le Rond d'Alembert (1717-1783) who first discovered the discrepancy. The reason d'Alembert's ideal theory failed to explain the true aerodynamic behavior of a sphere is that he ignored the influence of friction in his calculations. The actual flowfield around a sphere looks much different than his theory predicts because friction causes a phenomenon known as flow separation. We can better understand this effect by studying the following diagram of the actual flow around a smooth sphere. Here we see that the flowfield around the sphere is no longer symmetrical. Whereas the flow around the ideal sphere continued to follow the surface along the entire rear face, the actual flow no longer does so.

When the airflow follows along the surface, we say that the flow is attached. The point at which the flow breaks away from the surface is called the separation point, and the flow downstream of this point is referred to as separated. The region of separated flow is dominated by unsteady, recirculating vortices that create a wake. (a) Actual separated flowfield around a sphere and (b) the resulting pressure distribution The cause of this separation can be seen in the above pressure distribution around the sphere. As the flow moves downstream from the θ=90� or θ=270� position, it encounters an increasing pressure. Whenever a flow encounters increasing pressure, we say that it experiences an adverse pressure gradient. The change in pressure is called adverse because it causes the airflow to slow down and lose momentum. As the pressure continues to increase, the flow continues to slow down until it reaches a speed of zero. It is at this point that the air no longer has any forward momentum, so it separates from the surface. Once the flow separates from the surface, it no longer results in the ideal pressure distribution shown as the dashed line. Instead, a separated flow creates a region of low pressure in the wake.

We see this behavior over the rear face of the sphere from 90� < θ < 270� . Here, the actual pressure distribution, shown as the solid line, remains negative, in contrast to the ideal prediction. The pressure on the front face is still high, however, just as it was for the ideal sphere. Since the pressure is now much higher on the front face than it is on the rear face, the net result is a drag force exerted on the sphere. By accounting for the effect of friction, theory and experiment come into agreement and d'Alembert's Paradox is reconciled. This explanation leads us to an important conclusion: the drag on a sphere is dominated by the flow separation over its rear face. If we could somehow minimize that separation, the drag experienced by the sphere would be significantly reduced. We can see this effect in experimental data, like that pictured below. Variation of drag coefficient with Reynolds number for a sphere This diagram illustrates how the drag of a sphere varies with the Reynolds number .

Reynolds number (Re) is an important non-dimensional parameter that is used to relate the size of an object to the flow conditions it experiences, and is defined by the equation where l = reference length (in the case of a sphere, this variable is defined as the diameter) μ = viscosity (or friction) In other words, any two spheres that experience the same Reynolds number should exhibit the same aerodynamic characteristics even if the spheres are of different sizes or flying at different speeds. The above figure indicates that there is a significant change in the drag on a smooth sphere at a Reynolds number of about 3x105. Below this Re, the drag coefficient is roughly constant at 0.5. Above this Re, the drag coefficient again becomes nearly constant at about 0.1. What is it about this particular Reynolds number that causes such a large reduction in drag? It turns out that it is at this critical point that the air flowing around the sphere makes an important change. We have already discussed the concept of flow separation. One of the key factors affecting flow separation is the behavior of the boundary layer. The boundary layer is a thin layer of air that lies very close to the surface of a body in motion.

It is within this layer that the adverse pressure gradient develops that causes the airflow to separate from the surface. At low Reynolds numbers, the boundary layer remains very smooth and is called laminar. Laminar boundary layers are normally very desirable because they reduce drag on most shapes. Unfortunately, laminar boundary layers are also very fragile and separate from the surface of a body very easily when they encounter an adverse pressure gradient. This separated flow is what causes the drag to remain so high below the critical Reynolds number. At that Reynolds number, however, the boundary layer switches from being laminar to turbulent. The location at which this change in the boundary layer occurs is called the transition point. A turbulent boundary layer causes mixing of the air near the surface that normally results in higher drag. However, the advantage of turbulence is that it speeds up the airflow and gives it more forward momentum. As a result, the boundary layer resists the adverse pressure gradient much longer before it separates from the surface. Flow separation on a sphere with a laminar versus turbulent boundary layer The difference in the flowfields around a smooth sphere and a rough, or dimpled, sphere can be seen above.

Since the laminar boundary layer around the smooth sphere separates so rapidly, it creates a very large wake over the entire rear face. This large wake maximizes the region of low pressure and, therefore, results in the maximum difference in pressure between the front and rear faces. As we have seen, this difference creates a large drag like that seen below the transition Reynolds number. The transition to a turbulent boundary layer, on the other hand, adds energy to the flow allowing it to remain attached to the surface of the sphere further aft. Since separation is delayed, the resulting wake is much narrower. This thin wake reduces the low-pressure region on the rear face and reduces the difference in pressure between the front and back of the sphere. This smaller difference in pressure creates a smaller drag force comparable to that seen above the transition Reynolds number. These results tell us that causing a turbulent boundary layer to form on the front surface significantly reduces the sphere's drag. For a given sphere diameter, a designer has only two options encourage this transition, either 1) increase the speed of the flow over the sphere to increase the Reynolds number beyond transition or 2) make the surface rough in order to create turbulence. The latter case is often referred to as "tripping" the boundary layer.

In the case of a golf ball, increasing the speed is not an option since a golfer can only swing the club so fast, and this velocity is insufficient to exceed the transition Reynolds number. That leaves tripping the boundary layer as the only realistic alternative to reducing the drag on a golf ball. The purpose of the dimples is to do just that--to create a rough surface that promotes an early transition to a turbulent boundary layer. This turbulence helps the flow remain attached to the surface of the ball and reduces the size of the separated wake so as to reduce the drag it generates in flight. When the drag is reduced, the ball flies farther. Some golf ball manufacturers have even started including dimples with sharp corners rather than circular dimples since research indicates that these polygonal shapes reduce drag even more. Comparison of flow separation and drag on blunt and streamlined shapes The reason we do not see dimples on other shapes, like wings, is that these particular forms of boundary layer trips only work well on a blunt body like a sphere or a cylinder. The most dominant form of drag on these kinds of shapes is caused by pressure, as we have seen throughout this discussion.

More streamlined shapes like the airfoils used on wings are dominated by a different kind of drag called skin friction drag. These streamlined bodies, like that pictured above, have a teardrop shape that creates a much more gradual adverse pressure gradient. This less severe gradient promotes attached flow much further along the body that eliminates flow separation, or at least delays it until very near the trailing edge. The resulting wake is therefore very small and generates very little pressure drag. However, there do exist other types of devices commonly used on wings that create a similar effect to the dimples used on golf balls. Though these wing devices also create turbulence in order to delay flow separation, the purpose is not to decrease drag but to increase lift. One of the most popular of these devices is the vortex generator . A Gloster Javelin showing the three sets of vortex generators located along the outer portion of the wing Vortex generators are often placed along the outer portion of a wing in order to promote a turbulent boundary layer that adds forward momentum to the flow. As in the case of the golf ball, this turbulent boundary layer helps the flow overcome an adverse pressure gradient and remain attached to the surface longer than it would otherwise.

Flow visualization test on the leading edge extension of an F-18 A related device that is most commonly used on high performance fighters is the leading edge extension (LEX), like that shown above. Both the vortex generator and the LEX are primarily used to delay the flow separation that occurs when operating at high angles of attack near stall. As angle of attack increases, the adverse pressure gradient along the airfoil becomes increasingly stronger. Once the stall angle is reached, the gradient becomes so strong that it forces the flow to separate resulting in a loss of lift or control effectiveness. The advantage of devices like vortex generators and leading edge extensions is that they force the flow to remain attached at higher angles of attack and increase the stall angle. This improvement gives planes likes fighters greater maneuverability while increasing the safety of commercial airliners. - answer by Jeff Scott , 13 February 2005 Related Topics: Why do golf balls have dimples? | HowStuffWorks Why do golf balls have dimples? NEXT PAGENEXT The reason why golf balls have dimples is a story of natural selection .

Originally, golf balls were smooth; but golfers noticed that older balls that were beat up with nicks, bumps and slices in the cover seemed to fly farther. Golfers, being golfers, naturally gravitate toward anything that gives them an advantage on the golf course, so old, beat-up balls became standard issue. At some point, an aerodynamicist must have looked at this problem and realized that the nicks and cuts were acting as "turbulators" -- they induce turbulence in the layer of air next to the ball (the "boundary layer"). In some situations, a turbulent boundary layer reduces drag. Up Next What is the world's longest golf course? If you want to get deeper into the aerodynamics, there are two types of flow around an object: laminar and turbulent. Laminar flow has less drag, but it is also prone to a phenomenon called "separation." Once separation of a laminar boundary layer occurs, drag rises dramatically because of eddies that form in the gap. Turbulent flow has more drag initially but also better adhesion, and therefore is less prone to separation.

Therefore, if the shape of an object is such that separation occurs easily, it is better to turbulate the boundary layer (at the slight cost of increased drag) in order to increase adhesion and reduce eddies (which means a significant reduction in drag). Dimples on golf balls turbulate the boundary layer. The dimples on a golf ball are simply a formal, symmetrical way of creating the same turbulence in the boundary layer that nicks and cuts do. Here are some interesting links: Golf Ball Facts - Reasons Golf Balls Have Dimples Basic PLUS Author | 6,777 Articles Joined: May 14, 2006 Golf Ball Facts - Reasons Golf Balls Have Dimples By Abhishek Agarwal | Submitted On November 06, 2008 3 When you picture the golf ball in your mind, you imagine a small white solid ball with lot s of indented marks on them. This is unique to golf balls and these indented areas are what help a player control a golf ball in flight, in other words they give better control to the player. These indentations are also called golf ball dimples.

Dimples were first used on the golf balls around a century ago. This is after many players reported that damaged balls seemed to travel so much further than brand new ones. After they reported this, companies started making the balls in odd shapes to help them get this effect. One William Taylor spent a lot of time studying golf ball shapes and their paths in flight, and he is who perfected the dimples that are common on every golf ball that you will see today. The lift and the drag are the two forces of aerodynamics that affect the course of a golf ball in flight. The indentations or dimples allow air flow to be smooth over the golf ball so that the fraction is at minimum. The dimples help decrease the drag effect and also increase the lift effect. As a result, the ball travels faster and further, thanks to these dimples. The normal number of indentation on a golf ball in America is around three hundred and thirty six, but it is between three hundred and five hundred all around the world. Whatever the manufacturer, golf balls tend to have an even number of dimples on them with the exception of only one variety that has three hundred and thirty three.

We often hear of pros ordering a set of balls with a specific number of dimples. The number of dimples as well as their depths is what affects the ball in flight, and so much has been written and researched on the topic. Golf rules allow that the upper limit of area of the ball that can be made up of dimples as eighty percent, regardless of the number of them, which can even be a thousand. The largest number of dimples that has been put on record is one thousand and seventy. Research shows us that a perfect golf ball with the right number of dimples (around three hundred) can and does travel about twice the distance as a smooth ball without any indentations on the surface. Keeping that in mind, it is no wonder that pros ask for a specific number of dimples on their balls. The wooden ball of yesteryear has metamorphosed into what we today commonly see as the solid golf ball with all these dimples on it. This is thanks only to study and research. Abhishek is an avid Golfing enthusiast and he has got some great Golfing Secrets [ up his sleeves!

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Question: What are the small indentations on a golf ball called?
Answer: Dimples